Small and simple cookie banner, uses a bit of PHP, JavaScript/jQuery and some CSS for styling the banner.

gistfile1.php

<?php if(!isset($_COOKIE["comply_cookie"])) { ?>
  <div id="cookies">
  <p>Our website uses cookies. By continuing we assume your permission to deploy cookies, as detailed in our <a href="yourPolicy">privacy policy</a>.
  <span class="cookie-accept" title="Okay, close"><img src="img/close.png" alt="Close"/></span></p>
  </div>
<?php } ?>

gistfile2.js

$('.cookie-accept').click(function () { //on click event
  days = 182; //number of days to keep the cookie
  myDate = new Date();
  myDate.setTime(myDate.getTime()+(days*24*60*60*1000));
  document.cookie = "comply_cookie = comply_yes; expires = " + myDate.toGMTString(); //creates the cookie: name|value|expiry
  $("#cookies").slideUp("slow"); //jquery to slide it up
});


//---

document.getElementById("cookie-accept").onclick = function(e) {
  days = 182; //number of days to keep the cookie
  myDate = new Date();
  myDate.setTime(myDate.getTime()+(days*24*60*60*1000));
  document.cookie = "comply_cookie = comply_yes; expires = " + myDate.toGMTString(); //creates the cookie: name|value|expiry
  document.getElementById("cookies").parentNode.removeChild(elem);
}

gistfile3.css

#cookies { 
  width: 100%;
  margin: 0;
  padding: 0.5em 10%;
  background: rgba(86,86,86,0.95);
  border-bottom: solid 1px rgb(225,225,225);
}
 
#cookies p {
  font-family: sans-serif;
  font-size: 14px;
  font-weight: 700;
  letter-spacing: 1px;
  text-shadow: 0 -1px 0 rgba(0,0,0,0.35);
  text-align: center; 
  color: rgb(255,255,250);
  margin: 4px;
  z-index: 999;
}

#cookies .cookie-accept {
  padding-left: 10px;
  cursor: pointer;
  display: inline;
  color: rgb(255,255,250);
  text-shadow: 0 -1px 0 rgba(0,0,0,0.35);
}